The present invention relates to a machine tool and a method for cutting machining of workpieces, and in particular for cutting machining of metallic workpieces.
DE 196 35 258 C1 discloses a machine tool having a tool spindle which is arranged on a travelling column. The tool spindle in this case points with its tool downwards and it can be moved in three spatial axes perpendicular to one another. Below the tool spindle, there is arranged a workpiece carrier in the form of a workpiece spindle. The workpiece spindle receives and holds rod-shaped workpieces, and it can be pivoted about a pivot axis, so that a workpiece rod can be brought both into a horizontal and into a vertical position. In addition, the workpiece rod can be rotated about its longitudinal axis, so that a 5-axis-machining of the workpiece rod is enabled. By means of this known machine tool, a plurality of workpieces can be produced from the rod. In a development, which, however, is mentioned only briefly in DE 196 35 258 C1, the known machine tool has a second workpiece carrier, by means of which a partly machined workpiece can be extracted from the workpiece spindle in order to allow a machining of what is known as the sixth side, that is to say that side of the workpiece which was formerly chucked in the first workpiece spindle.
DE 100 29 967 A1 discloses a machine tool for the machining of optical workpieces, which machine tool has two tool spindles arranged next to one another and two workpiece spindles arranged next to one another, wherein a tool spindle and a workpiece spindle in each case are located opposite one another in order machine workpieces. A direct transfer of a partly machined workpiece from one workpiece spindle to the other is neither provided nor possible. For 6-side machining, therefore, a partly machined workpiece has to be rechucked from one workpiece carrier onto the other workpiece carrier, and this may be detrimental to machining accuracy due to position errors during the rechucking operation.
Machine tools having a plurality of working spindles are known from DE 33 20 940 A1 and DE 203 01 126 U1. DE 33 20 940 A1 relates to a two-spindle lathe, the two working spindles (=workpiece spindles in this case) being arranged so as to be offset at 180° with respect to one another, in order to allow a transfer of a partly machined workpiece from one working spindle to the other. However, the known machine allows only lathe-turning machining of workpieces, that is to say it is limited in terms of machining flexibility and the complexity of the workpieces produced.
A machine tool disclosed by DE 203 01 126 U1 is designed for simultaneous machining of two identical workpieces in two parallel chucking fixtures. The transfer of a (partly machined) workpiece from one workpiece carrier to the other is neither provided nor possible. Accordingly, the machining accuracy of this known machine tool in the case of 6-side machining is limited.